Without changing anything, you can use "-" as your input and output filenames when piping between scripts, which open inteprets as wanting to use STDIN or STDOUT depending on context.

  perl ./program1 prog1.input - \
| perl ./program2 - -           \
| perl ./program3 - prog3.output

etc
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Even better would be to add some logic to your scripts so that they defaulted to "-" automatically if filenames were absent, and then you could do ...

  perl ./program1   prog1.input \
| perl ./program2               \
| perl ./program3 > prog3.output

etc
[download]

    --k.